Add ability to display additional information from PNG image files

Submitted by Jason

Assigned to Steve Dodier-Lazaro

Link to original bug (#10321)

Description

In a similar vein to displaying EXIF data for JPEGs, display data from PNG chunks for PNG image files.

Various chunk types are listed in the PNG specification here:

http://www.libpng.org/pub/png/spec/register/pngreg-1.3.0-pdg.html

In particular, display the tEXt and zTXt chunks in a suitable property page.

I'd have a go myself at this, but not being familiar with GTK nor XFCE programming it would take me longer than an expert. If someone were to give some hints, I'd be grateful. (Downloaded the GIT repository for XFCE, built it, no further yet.)